Due to corruption it is prompting so but you can retrieve all files and data from your Western Digital Passport(450Gb) after the format with the help of an efficient data recovery software. I will suggest you Kernel for FAT and NTFS hard disk data recovery software for the recovery of your files and data from it. The software will scan your hard drive after you format it, and then it will preview you the all files before format, it gave you the choice to save all files at once or some selective files to your location. for more details - Hard disk data recovery software.